The objective of this project is to investigate extracellular matrix-cell interactions employing an experimental system of matrix-induced endochondral bone formation. Subjects currently under active investigation are: (1) transitions in collagen and proteoglycans during bond development; (2) hormonal and nutritional influences on bone formation; and (3) modes of interaction between collagenous matrices and cells. BIBLIOGRAPHIC REFERENCES: Reddi, A.H. and Anderson, W.A.: Collagenous bone and matrix-induced endochondral ossification and hemopoiesis. J. Cell Biol. 69: 557-572, 1976. Reddi, A.H. and Huggins, C.B.: Hormone-dependent haematopoiesis in fibroblast-transformation ossicles. Nature 263: 514-515, 1976.